Help With '74 Concert Bass!

[FranF]

Hi. Been a while since my last post! Anyway, I have a '74 CB that needs preamp circuit board work. It was fine until I was A/B-ing both it and my B-15 (ungrounded). Well, touched bass and both amps at once, since I was shutting down the CB, and apparently I cooked something in the pre. It still comes on, pops, etc., just no sound. I hooked up a cd player to the inputs and can trace sound through several components on the pc board until I get to what's probably the cooked one, be it a resistor or transistor???  My question is, since I'm pretty sure it can be repaired, is there anyone here I can send it to for a reasonable repair? I'll gladly remove the pc board and ship it to someone. Can anybody make a recommendation? Thanks!

[FranF]

Anybody?

[FranF]

Just hoping somebody takes a stab at this before the site closes!

[JoeArthur]

The best advice I can give you is to take the amp - the whole amp, to a tech in your area and get it repaired.

No tech in their right mind is going to accept a circuit board for a repair.  Put yourself in the place of a tech and consider these points.  

o Some user wants to extract a circuit board and send it to you.  This user admits he doesn't know the difference between a transistor and a resistor but claims he has diagnosed the problem.  

o The amp has long been out of production.  Do you have or can you get the schematic?

o Even with a schematic, you notice that this circuit board has several different voltage and polarity supply requirements to get it to operate.  Without the amp's power supply, how are you going to power up the circuit board with the correct voltage and polarity to either verify the diagnosis or test it after replacing parts?

o This preamp board has a bunch of external connections.  Did the user mark where every one of them went?  Do you have confidence it will be replace correctly or do you think something like this is going to happen?

http://www.dangpow.com/~sunn/phpBB2/viewtopic.php?t=2198

o What are you going to do when the user contacts you and says his amp doesn't work?  How much time and other resources are you going to be willing to help the guy out?

Just a few thoughts.

[FranF]

Excellent points! Just thought maybe it was an easily recognizable problem. Around here, like maybe many other locales, there's a shortage, if not total absence of knowledgeable techs. I'll gladly send the whole amp to someone who knows their way around 70s transistor amps.